Pls help solve this question (Radiometry dating)

Calculate the age of a mineral using
235U decaying to 207Pb. Half-life is 713
million years. A laboratory determines
that, at present, there are 440,000 atoms
of 235U and that the amount of 207Pb
indicates that when the mineral
crystallized, there were 1,200,000 atoms
of 235U. (Assume there was no 207Pb in
the mineral at the time the mineral
crystallize).
Note: U= Uranium, Pb= Lead.